Clay has long been used as a liquid absorbent, and has found particular usefulness as an animal litter.
Because of the growing number of domestic animals used as house pets, there is a need for litters so that animals may micturate, void or otherwise eliminate liquid or solid waste indoors in a controlled location. Many cat litters use clay as an absorbent. Typically, the clay is mined, dried, and crushed to the desired particle size.
Other absorbent materials that are used alone, in combination, or in combination with clay include straw, sawdust, wood chips, wood shavings, porous polymeric beads, shredded paper, bark, cloth, ground corn husks, cellulose, water-insoluble inorganic salts, such as calcium sulfate, silica gel and sand.
Some clay litters have the ability to clump upon wetting. For example, sodium bentonite is a water-swellable clay which, upon contact with moist animal waste, is able to agglomerate with other moistened sodium bentonite clay particles. The moist animal waste is contained by the agglomeration of the moist clay particles into an isolatable clump, which can be removed from the container (e.g., litterbox) housing the litter. However, the clump strength of clay litters described above is typically not strong enough to hold the clump shape upon scooping, and inevitably, pieces of the litter break off of the clump and remain in the litter box, allowing waste therein to create malodors. Further, raw clay typically has a high clump aspect ratio when urinated in. The result is that the wetted portion of clay will often extend to the container containing it and stick to the side or bottom of the container.
Illustrative bentonite based litter compositions are disclosed in U.S. Pat. Nos. 5,503,111; 5,386,803; 5,317,990; 5,129,365 and RE 33,983, which are hereby incorporated by reference in their entirety.
Additives, such as starch or sugar based binders can be added to non-bentonite clays to create a litter material that behaves like a bentonite clay, i.e., upon contact with liquid (or moist) dross, readily agglomerates with other moistened clay particles. U.S. Pat. No. 5,359,961 discloses a clumping non-swelling clay based litter and is hereby incorporated by reference in its entirety.
What is needed is an absorbent material suitable for use as a cat litter/liquid absorbent that has better clumping characteristics, i.e., clump strength and aspect ratio, than absorbent materials heretofore known.
Another problem inherent in typical litters is the inability to effectively control malodors. Clay has very poor odor-controlling qualities, and inevitably waste build-up leads to severe malodor production. One attempted solution to the malodor problem has been the introduction of granular activated carbon (GAC) (20-8 mesh) into the litter. However, the GAC is usually dry blended with the litter, making the litter undesirably dusty. Other methods mix GAC and clay and compress the mixture into particles. In either case, the GAC concentration must typically be 1% by weight or higher to be effective. GAC is very expensive, and the need for such high concentrations greatly increases production costs. Further, because the clay and GAC particles are merely mixed, the litter will have GAC agglomerated in some areas, and particles with no GAC.
The human objection to odor is not the only reason that it is desirable to reduce odors. Studies have shown that cats prefer litter with little or no smell. One theory is that cats like to mark their territory by urinating. When cats return to the litterbox and don't sense their odor, they will try to mark their territory again. The net effect is that cats return to use the litter box more often if the odor of their markings are reduced.
Agglomeration processes have been around for decades. However, most agglomeration processes result in compacted agglomeration products with bulk densities equal to or higher than the raw feed material. Shipping costs of these agglomeration products often results in higher costs to the manufacturer due to the increase in weight.
Another problem with typical agglomeration processes is that the compaction used produces dense agglomerated materials that lack porosity, which results in limited utility.
What is needed is an absorbent material with improved odor-controlling properties, and that maintains such properties for longer periods of time.
What is further needed is an absorbent material with odor-controlling properties comparable to heretofore known materials, yet requiring much lower concentrations of odor controlling actives.
What is still further needed is an absorbent material with a lower bulk density while maintaining a high absorbency rate comparable to heretofore known materials.